Certainly. Each version has a different pattern added to the background. One of them is patterned with stripes, the other with halftone. It's subtle, but definitely noticeable when viewing the full-size image.

The reason for uploading two different types is that when I was asking people for feedback before uploading, the consensus was literally 50/50 on which background they preferred.

While it may not have suited you or what you wanted for the image, I think making a small space between "Night" and "Day" and making that "Twilight" would make this perfect (Of course, add Twilight in there as well )

Luna and Celestia in this wallpaper is a vectored image that was made by someone else ([link]).

A vector is basically a series of shapes (or "paths" as they are called in programs) that can be resized without any loss of quality. Vector artists will typically upload a large PNG image of the vector (which can be scaled down, but not up since it is converted from vector based to bitmap based) and will also sometimes include a download of the vector file so that others can modify it. A vector file is usually an SVG (Inkscape) or AI (Adobe Illustrator) file.